Projectile



y 1961 N. A. WALKER 2,983,225

PROJECTILE Filed June 30, 1944 FIG. 2

INVENTOR w WALKER A RNEY PROJECTILE Nelson A. Walker, Santa Fe, N. Mex.,assignor, by mesne assignments, to the United States of America asrepresented by the Secretary of the Navy Filed June 34 1944, Ser. No.542,911

1 Claim. (Cl. 102-93) This invention relates to subcaliber projectilesof the type which comprises a subcaliber core having full cahbersupporting and centering means releasable from the core when theprojectile emerges from the gun barrel. More particularly, the inventionhas reference to a novel projectile of the character described having agenerally cup-shaped supporting and centering means releasable from thecore by reverse setback in the initial flight of the projectile after itemerges from the gun.

It has been proposed heretofore to fit the rear end portion of aprojectile core into a cup-shaped sabot'acted upon by the powderpressure in the gun barrel and designed to release from the core whenthe projectile leaves the gun muzzle. However, this type of projectileas previously constructed is unsatisfactory for various reasons, amongwhich are its dependence upon both centrifugal force and reverse setbackfor release of the sabot, the tendency for the core to become wedged inthe sabot under setback so that release of the sabot from the core isuncertain, and serious disturbance of the core flight incident torelease of the sabot.

One object of the present invention, therefore, resides in the provisionof a sabot type projectile comprising a subcaliber core fitted closelyat its rear end into a cupshaped sabot which is positively discardedfrom the core by reverse setback, without seriously disturbing theflight of the core.

Another object of the invention is to provide a projectile of thecharacter described in which the cup-shaped sabot carries a turning bandfor imparting rotation to the core by action of the gun ri-fling.

A further object is to provide a projectile of the character describedin which the cup-shaped sabot has a tapered fit over the rear endportion of the core for centering the core in the sabot and avoidingdisturbance of the core flight due to releaseof the sabot.

Still another object of the invention resides in the provision of aprojectile of the character described in which the cup-shaped sabot andthe core have complementary parts for positively limiting the wedgingaction of the core in the tapered portion of the sabot under setbackwhen the projectile is fired from a gun.

An additional object is to provide a sabot type projectile-comprising asubcaliber core, a cup-shaped sabot in which the rear end portion of thecore is closely fitted, and a sleeve-like bourrelet fitted closelyaround the core and part of the sabot, the front end of the bourreletbeing open whereby the bourrelet and sabot are slidable off the rear endof the core as a unit under reverse setback.

These and other objects of the invention may be better understood byreference to the accompanying drawing, in which:

Fig. 1 is a longitudinal sectional view of a projectile made inaccordance with the invention, and

Fig. 2 is a view in side elevation of the cup-shaped sabot shown in Fig.1.

Referring to the drawing, the projectile there shown comprises asubcaliber core which may be made of Patented May 9, 1961 steelsubjected to suitable treatment for hardening. At its front end portion,the core 10 has an ogive 10a, and directly to the rear of the ogive thecore is tapered slightly toward the base of the projectile, as shown at10b, the taper extending over the major portion of the On the rear endportion of the core 10 is a substantially full caliber sabot 13, whichmay be made of steel, or the like. The front face of the sabot 13 at itscentral portion is flat, as shown at 14, and fits closely against theflat base of the projectile core, the sabot surface 14 and the adjacentcore surface being disposed in a plane normal to the core axis. A hollowboss 15 projects forward-1y from the front faceof sabot 13 into anannular space 13a between the core 1% and bourrelet, and surrounds thefiat surface 14 of the sabot, the boss being preferably integral withthe sabot. The inner surface of the boss 15 is tapered toward the flatface 14, as shown at 16, whereby the abruptly tapered portion 11 of thecore is closely received in the. boss. However, a slight clearance isprovided between thetapered side wall 16 of boss 15 and said abruptlytapered portion 11 of the core, providing an oversize socket for apurpose to be described presently. The sabot 13 extends radiallyoutwardly beyond the boss 15 to provide a shoulder, the front face 17 ofwhich is flat and lies in the same plane as the sabot face 14. At itscentral portion, the sabot has an opening 18 extending through the sabotfor the passage of powder gases from a tracer charge (not shown) in therear end portion of the core.

A unitary substantially full caliber sleeve-like bourrelet 20 is fittedclosely around the intermediate tapered portion 1% of the projectilecore, the inner surface of the sleeve being tapered to complement thetaper 10b. Near its rear end, the bourrelet 20 has an internal shoulder21 engaging the front end of the sabot boss 15. To the rear of theshoulder 21, the bourrelet is fitted closely around the externalcylindrical surface of boss 15, the rear end of the bourrelet beingseated against the front face 17 of the sabot shoulder.

The sabot 13 is externally grooved on its cylindrical surface, as shownat 23. A turning band 24, which may be made of annealed copper, ispress-fitted on the grooved portion 23 and bears against the rear end ofbourrelet 20. The band 24 has an external diameter somewhat greater thanthat of the cylindrical sleeve 20, so that the band is adapted to beengraved by the usual rifling in the gun barrel to impart rotation tothe projectile. The turning band may be screwed instead of press-fittedon the sabot, in which case it will be understood that the thread is insuch a directionthat rotation of the turning band 24 by the rifling actsto tighten the band on the sabot. The components 13, 2t and the turningband 24 comprise what .is conveniently termed a sabot assembly which, aslater appears, is adapted to he slid from the core in one piece.

The operation of the projectile is as follows:

When the projectile is fired from a gun, the pressure of the powderpropellant acts upon the relatively large area of the sabot 13 andturning band 24. As the projectile moves along the gun barrel, the forceof setback on the upon it by the sabot 13 and bourrelet 20.

An important feature of the present invention is the relatively sharptaper 11 at the extreme rear end portion of the core and in the sabotboss 15. In this conneotion, it has been found that in prior projectileshaving a conventional cup-type sabot, the latter cannot be made torelease from the core without seriously disturbing the flight of thecore, this disturbance being manifested by the core tumbling in flight.The P ecise reason for such disturbance is not clear. However, I havefound that by abruptly tapering the extreme rear end portion of the corewhere it fits into the oversize socket of the sabot boss, a clean breakoccurs between the core and sabot assembly whereby this disturbance atrelease may be avoided. The release is further facilitated by the slighttaper betweenthe core and bourrelet. As soon as the sabot and bourreletstart to slide back, the core is pletely free of the surroundingstructures.

With the tapered fit between the core and the sabot boss, it isessential that the core be prevented from wedging into the taperedportion of the boss under setback incident to acceleration of theprojectile, because any such wedging action would interfere with therelease of the sabot and bourrelet from the core when the projectileemerges from the gun muzzle. In the new projectile, wedging of the corein the sabot boss is prevented because of the clearance maintainedbetween the core and the tapered portion of the boss by engagement ofthe flat base of the bore with the surface 14 of the sabot. Thus, thebearing surface during setback is on the base of the core and not on itstapered portion 11.

It will be understood that the torque incident to rotation of theturning band 24 by the gun rifling is transmitted to the coreprincipally through the sabot 13 but to some extent through thebourrelet also. In this connection, the force of setback of the coreagainst the sabot face 14 due to acceleration of the projectileincreases the pressure and therefore the friction between the sabot andcore, whereby the torque transmission is facilitated. Also, the setbackforce of the bourrelet 20 on the sabot increases the pressure andfriction between these parts so that the bourrelet is better adapted totransmit torque from the turning band and sabot to the core comwithoutlost motion. It will be noted that the sabot and bourrelet are releasedas one piece. This piece follows the same trajectory as the core atfirst, but due to unfavorable aerodynamic shape the range is less. Inmany subcaliber constructions the disoardable portions are releasedcentrifugally, the fragments causing a hazard to personnel in front ofthe gun. Since the discardable portion in the present invention is inone piece which goes in the same direction as the core, this hazard isreduced to a minimum.

I claim:'

A subcaliber projectile comprising, a subcaliber core having an ogive atone end thereof and being inwardly tapered slightly from said ogivetowards the other end thereof, said other end of said core having anabruptly tapered terminal portion and a base normal to the axis of saidcore, a sabot assembly mounted on the core, said assembly comprising afull caliber, open-ended, internally tapered bourrelet fitted closelyaround the core with its forward end terminating adjacent the rear ofsaid ogive, the rearward end of said bourrelet terminating approximatelyin the plane of the base of said core and having an internal annularrecess, the axial length of said recess being substantially the same asthe axial length of said abruptly tapered terminal portion, and a sabothaving a boss fitted tightly in said recess and having surfaces firm- 1yabutting the end of the bourrelet and the base of the core, said bosshaving a tapered socket receiving said abruptly tapered terminal portionof said core, said tapered socket having cross-sectional dimensionslarger than the cross-sectional dimensions of said abruptly taperedterminal portion of said core, thereby providing a clearance betweensaid socket and said terminal portion; whereby the core is preventedfrom wedging into the tapered portions of the sabot assembly undersetback incident to acceleration of the projectile, and a clean breakbetween the sabot assembly and the core of the projectile is assuredupon firing of the projectileunder reverse setback incident toaerodynamic drag on the sabot assembly.

References Cited in the file of this patent UNITED STATES PATENTS 29,272Hotchkiss July 24, 1860 1,973,604 Brandt Sept. 11, 1934 2,306,140 ReedDec. 22, 1942 FOREIGN PATENTS 496,879 France Aug. 20, 1919 131,034 GreatBritain Aug. 21, 1919 812,680 France Feb. 8, 1937

